bild

Small intestine. Light micrograph of a section through the ileum, the final section of the small intestine. The lumen (white, top right) is lined with villi (purple). Below this is a layer of smooth muscle (orange) and then a layer of circular and longitudinal muscles (pink). Magnification: x40 when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER)